1. Field of the Invention
The present invention relates to an image forming apparatus and an image processing method for optimizing image correction conditions, and to a recording medium therefor.
2. Description of the Related Art
In image recording apparatuses for recording and outputting an image, the image quality (in particular, gradation characteristics) of the output image becomes unstable due to various factors. In particular, in color recording apparatuses, variations of gradation are often noticeable.
For example, in a recording apparatus using an electro-photographic method in which color toner is used as a coloring material, variations of apparatus parts, such as light-emission characteristics of a laser, and photosensitive characteristics of a photosensitive body, and variations in printing characteristics due to environmental variations such as temperature, humidity, etc., are factors resulting in unstable image quality.
As methods for correcting such instability of image quality, several methods have been conventionally conceived. For example, in a recording apparatus taking the form of, for example, a copier, a monochromatic gradation patch of each of the CMYK colors (cyan, magenta, yellow, and black) is printed and is read by a reader, and a one-dimensional gradation correction table such as that having predetermined gradation characteristics is produced for each of the CMYK colors, and this is used for gradation conversion (xcex3 conversion).
In another example, a copier is used as a printer. In this case, gradation conversion using this gradation correction table is performed on multi-valued data sent from a printer controller.
Recently, from the viewpoint of cost and in order to reduce the load on a bus, the number of systems in which a printer controller forms image data into binary values and then sends them to a print engine, and the print engine performs binary recording based on the received binary data is increasing.
In such a case, since binary data is received from the printer controller, it is not possible for the print engine to correct the gradation. Also, when the binarization method differs between when it is used as a copier and when it is used in a printer, the printer controller must perform its own gradation correction corresponding to the binarization method performed by the printer controller. Accordingly, since a conventional printer controller which does not have the function for producing a gradation correction table produces a gradation correction table on the basis of manual instructions from a user, the user is required to perform a complex operation.
It is an object of the present invention to stabilize image quality in both a copier mode and a printer mode without placing a significant burden on a user.
To achieve the above-mentioned object, according to a first aspect of the present invention, there is provided an image forming apparatus comprising: a reading unit for reading an original document and producing first image signals; an input unit for inputting second image signals from an external apparatus; an image forming unit for forming an image on a recording medium on the basis of the first and second image signals produced by the reading unit and input by the input unit, respectively; a calibration unit for calibrating image processing conditions corresponding to image forming characteristics in a copier mode; and a production unit for producing image processing conditions in a printer mode on the basis of the calibrated image processing conditions. The image forming apparatus has the copier mode in which an image is formed by using the reading unit and the image forming unit and the printer mode in which an image is formed by using the input unit and the image forming unit.
It is another object of the present invention to easily produce image correction conditions corresponding to a different halftone method.
To achieve the above-mentioned object, according to a second aspect of the present invention, there is provided an image processing method for calibrating image correction conditions corresponding to each halftone process based on first and second halftone methods, the image processing method comprising the steps of: producing first image correction conditions corresponding to the first halftone method on the basis of pattern image signals which are obtained by reading a pattern image which is halftone-processed and output by the first halftone method; and producing second image correction conditions corresponding to the second halftone method from the first image correction conditions on the basis of the correlation between the first and second halftone methods.